Researchers hack femtocells, record mobile phones’ calls, SMS traffic

Intercepting voice calls, SMS messages, and web traffic coming and going from a target’s mobile phone may be as simple as waiting for his phone to associate to a hackable femtocell and then use it to spy on him or even clone his device, iSEC researchers warned at a demonstration at the Black Hat conference.

Before a packed auditorium, the security firm’s team demonstrated how a vulnerability in two femtocells widely deployed in the US by Verizon allowed them to compromise the device and use it to collect traffic coming to and from mobile phones connected to it.

Femtocells, those small cellular stations for extending the cell phone coverage range indoors or at the cell edge, are sold by carriers to private or business customers that have problems getting a good enough signal for their mobile phones or good voice quality when it comes to calls. They are usually plug-and-play, and work by creating an IPSec tunnel between themselves and the mobile operator’s network.

The vulnerability that was used by the researchers to collect and record all the aforementioned data and more from messages, voice calls and web traffic has been patched by Verizon, and the vulnerable femtocells in use have received a firmware update that resolved the issue.

Nevertheless, iSEC researchers believe that other similar attacks are sure to be discovered in the future – this is not the first time such a vulnerability was discovered, and it won’t be the last.

They advise carriers to drop femtocells altogether and switch to network level protection, especially because the victims would likely be unaware that it is happening as their phones automatically associate themselves to femtocells when in range.

“This is not like WiFi, you do not have a choice,” pointed out iSEC researcher Doug DePerry.

V3 reports that the company intends to release a free app that protects users from this or similar attacks by forcing the phone into Airplane Mode when it detects and tries to associate itself with a femtocell.